(1) The board of public utilities may, in their discretion and from time to time, make an enlargement or enlargements of the plants and systems and extensions of the lines thereof as may be necessary to serve the residents of the city or town with electric lights, electric power, water, or sewerage, whether the area to be so serviced shall be included in the improvement district or not.
(2) No additional tax shall be levied upon the property within the improvement district, but the funds for that purpose may be contributed in whole or in part by outside agencies, or by the persons to be benefited, or, in the discretion of the board, the funds may be taken from the net revenue coming into its hands.